Conventional cardiac pacemakers and defibrillators generally consist of a round disc shaped generator for electrical stimulation and an elongated flexible wire lead that is connected proximally to a header structure on the generator that is implanted subcutaneously for cardiac pacing and defibrillation. The cardiac lead is generally configured with tubular electrically insulated sleeve structures that are inserted into the body through an incision overlying veins leading to the heart chambers where the distal end of the lead is lodged. In such cases, the distal end of the lead is connected to a tubular tip electrode, having an increased diameter forming an annular shoulder against which the distal end of the sleeve abuts.
Biocompatible silicone based adhesives are generally used to connect the distal end of the lead sleeve and the tip electrode. Among the limitations of adhesives is that the manufacture of the assembled lead requires sufficient time for the adhesive to cure, and the adhesive's bond strength may decrease in time and permit separation from the tip electrode from the sleeve. Fixing the distal end of the lead to cardiac tissue is accomplished generally by conventional anchoring systems. One such active fixation mechanism involves a screw-in electrode. Further, a passive fixation mechanism is sometimes used, consisting of one or more radial tines that engage the inner lining of the heart or blood vessel.
Such conventional devices are typically employed and include a single chamber device as well as a dual chamber device. The single chamber device is capable of sensing and pacing in one chamber, either in the atrium or in the ventricle. Dual chamber devices have the capability of sensing and pacing in both chambers. Modes of pacing are designated, for example, VDD, DVI, VVI, and DDD, where the first letter of the mode indicates the chamber being paced, the second letter indicates the chamber being sensed, and the third letter indicates inhibited or triggered responses. A fourth letter “R” may denote rate responsive pacing to match a patient's activities. In addition to pacing the right/atrium and ventricle pacing, the left ventricle by way of the cardiac veins or biventricular pacing provides a physiologic and synchronous cardiac contraction which would improve cardiac function.
Generally speaking, there are two types of leads in the art: unipolar and bipolar leads. The unipolar lead has a single conductor coil, typically with a cathode, or negative pole, at the distal tip and an anode, or positive pole, defined by the housing of the stimulator. Electric current returns to the anode via body tissue as a current path. In opposition, a bipolar lead has two conductor coils, the distal tip forming the cathode and an annular or ring electrode located a few millimeters proximal to the distal tip. High voltage defibrillation is delivered by the one or two shocking coils that are inserted intravenously.
Pacemaker leads that have been used are generally suited for placement in the ventricle and atrium. In order to provide permanent pacing and to avoid pacemaker lead dislodgement, various methods have been used for anchoring the leads to the endocardium, the inner lining of the heart chambers.
Prior art leadless pacemakers include limitations wherein the devices require an anchoring system in the form of screws or tines. In particular, the Nanostim device (St. Jude Medical) uses a helical wire screw; while the Micra system (Medtronic) uses tines, and is delivered to the right ventricle by way of the femoral vein, having a reattachable mechanism for extraction. Such devices solely pace the ventricle and thus do not permit atrioventricular synchrony. In particular, the Micra transcatheter pacemaker is a single-chamber ventricular pacemaker that is self-contained in a hermetically enclosed capsule. The implantation procedure for the transcatheter pacemaker uses a steerable catheter delivery system and is inserted through a femoral vein by use of a 23-French introducer. Such leadless prior art devices do not supplant traditional lead-containing transvenous pacemakers, and are generally used only for single-chamber ventricular pacing. This procedure is generally reserved for patients with atrial fibrillation and bradycardia or for use in patients who only need infrequent pacing. Such prior art systems are not useful in the treatment of the majority of pacemaker recipients that include patients with sinus-node dysfunction or heart block and do not have a role in the treatment of patients with heart failure who need left-ventricular resynchronization for improvement of cardiac output. (M. S. Link, “Achilles' Lead: Will Pacemakers Break Free?” N. Engl. J. Med., Vol. 374, No. 6 (Feb. 11, 2016), pp. 585-586).
Other leadless pacemaker devices are shown in U.S. Pat. Nos. 5,814,089, 6,522,915, 6,584,352, 8,923,963, and 9,072,914. However, such prior art systems are generally not self-retaining and require fixation tines or helical fixation when inserted into a patient's body. Such prior art systems generally do not provide for an adjustable diameter size and have limited endothelial contact.
PCT Publication WO2004/045675 discloses an introducer through which a pacemaker lead is guided. This introducer is formed with a distal end comprising an anchor attached to the walls of the cardiac chambers. Through use of such prior art introducers, there is permitted steering of the pacemaker lead, and the pacemaker is prevented from displacements or folding onto itself due to the lack of support.
Another prior art system, U.S. Pat. No. 6,654,683, discloses an ultrasonically activated implantable cardiac electrode system, whereby piezoelectric elements convert mechanical energy into electrical energy sufficient to cause pacing of the cardiac tissue. Mechanical energy may originate from an external source low frequency ultrasound transmitter. The electrical energy produced by the piezoelectric element delivers pacing level electrical energy between the system's anode/cathode. Active fixation elements using tines, hooks, and barbs are provided. The prior art system does not use the data to send signals to a wireless curvilinear electrode configuration and thus, the curvilinear electrodes do not require a power source, since the generator functions as the sensing system and provides the logic necessary to synchronize the stimulation of tissues. An algorithm is used for determining the timing and sequence of stimulation of cardiac tissues for generators attached to the electrode wires embedded in the cardiac chambers.
Finally, U.S. Pat. No. 6,256,543 discloses a temporary pacemaker lead having a pair of connections with releasable engagement so as to permanently affix the electrode to the heart tissue. The electrode may be in the form of a piece of metal, such as a clip, and when the lead wire is removed from the heart, such is released from the electrode and may be reattached.